Diversity is a concept that reflects the presence of a wide variety of characteristics within a group or society. It involves differences in cultural, ethnic, linguistic, and social facets among people. This question seeks to understand the driving factor behind why diversity brings something new and different to a group or society.

Let's analyze the options:

1. Homogeneous population: A homogeneous population is one where members share similar traits and characteristics. Such populations tend to have less diversity since there is less variability in the cultural, ethnic, or social characteristics. Therefore, this is not conducive to diversity bringing something new or different.
2. Intermixing of cultures: This option refers to the blending of different cultural elements, beliefs, practices, and values within a society. Such intermixing usually results in increased diversity because it introduces new cultural ideas, customs, and innovations—hence, leading to fresh and varied perspectives. This aligns well with the idea that diversity brings something new and different.
3. Genetic composition: While genetic diversity is significant in biological contexts, particularly concerning the health and survival of populations, it is less directly relevant to the sociological context of cultural diversity. This factor is more about biological variability rather than societal or cultural differences.
4. Similarities and identical traits: If a population predominantly shares similar traits and attributes, it limits the scope of diversity. Similarities and identical traits might lead to uniformity rather than diversity, which is contrary to the concept of introducing something new and different.

Conclusion: Based on the analysis, the most appropriate option is Intermixing of cultures. This choice explains how diversity emerges with something novel and varied, driven by the convergence and blending of distinct cultural aspects.